Investigation of Factors Regulating the Biological Activity of Sertoli Cells in the Neonatal Boar Testis.

Abstract

The mechanisms governing the ontogeny of Sertoli cells during testis development in boars remains unknown. The objective of the current study was to determine the pattern of Sertoli cell maturation in porcine testis tissue and identify mechanisms governing the developmental plasticity of these cells. We hypothesize the existence of heterogeneous Sertoli cell populations in the boar testis characterized by two distinct phases of postnatal Sertoli cell maturation. To test this hypothesis, we (1) determined the proliferation kinetics of Sertoli cells in testis tissue from 3-, 7-, 14- and 20 day post partum boars in situ, (2) evaluated the developmental plasticity of these cells using the testis tissue xenografting approach at several time-points, and (3) assayed the expression of genes important for regulating the biological activity of Sertoli cells during the first three weeks of neonatal life. Immunohistochemical analysis of DDX4 and GATA4 expression were used as specific markers of germ and Sertoli cell populations for morphometric analysis. PCNA immunoreactivity demonstrated that Sertoli cells were mitotically active throughout pre-pubertal and postnatal testis development. The grafting bioassay indicated that approximately 30% of porcine Sertoli cells are mitotically active in 1-month post partum testis tissue, but this rate is significantly reduced (p<0.05, 2-fold) in 2, 3 and 5-month post partum testis tissue grafts. Testis tissues from 3-dpp donor boars contained a significantly greater percentage (p<0.05) of mitotically active Sertoli cells after 20-wks of grafting when compared to other donor ages evaluated in the study. qPCR analysis of biomarkers associated with Sertoli cell proliferation and differentiation (AR, THR-alpha, THR-beta, ER-alpha, KRT18) is consistent with mitosis and proliferation of Sertoli and germ cells in porcine testis xenografts. Taken together these findings support the hypothesis of heterogeneous populations of Sertoli cells in the boar testis underscored by critical maturation events which occur by 2-wks of age.